1. Field of the Invention
The present invention relates in general to a method and apparatus to pump material through a tubular using electrohydrodynamics and in particular to pumping drilling mud through a tubular using electrohydrodynamics.
2. Brief Description of Related Art
In earth-boring operations such as drilling wells for mineral recovery, drilling mud is pumped through a drill string and out into the wellbore from a point near the drill bit. The drilling mud lubricates the cutting surfaces of the drill bit and also moves the spoil from the drill bit up through the wellbore toward the surface. Pieces of rock and other abrasive materials are suspended in the drilling mud as the drilling mud rises to the surface.
For offshore wells, moving materials such as drilling mud, and cuttings suspended in drilling mud, up from the depths of the earth during drilling requires moving the materials up through two gradients. The first gradient being the distance from the drill bit to the sea floor and the second gradient being from the sea floor up through a riser pipe or casing the drilling rig. Drilling operations in deep water is sometimes referred to as “dual gradient drilling.”
In dual gradient drilling operations, static head pressure builds as the drilling mud is pumped to the surface. Significant pressure is required to move the drilling mud up through the wellbore against the head. The head pressure is further increased in deep water drilling operations because the drilling mud must also overcome the static head pressure in the riser as the mud moves from the mudline wellhead housing up to the rig on the surface of the water. The high injection pressure required to overcome the head pressure may result in damage to the riser or damage to the rock formation. Dual gradient drilling operations may use a separate mud return line for moving drilling mud upward through the sea to the drilling rig and thus reduce head pressure on the riser.
Head pressure in the rock formation can be reduced if the drilling mud is pumped up from the sea floor to the drilling rig, either through the riser or through a bypass. Various conventional pumping technologies have been tested to pump the drilling mud up through the riser or to pump the drilling mud through an external bypass tube that runs parallel to the riser. Unfortunately, the rock and abrasives in the drilling mud are very destructive to seals and moving parts associated with conventional pumps, resulting in frequent pump failures. A method of pumping drilling mud through a riser, that does not require a conventional pump is desired.